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HAROLD C. ROBINSON AND LEO F. RETTGER 



shaped forms, and very few typical diplococci. On the other 

 hand, the stains from the opsine cultures contained very few 

 involution forms, and were almost indistinguishable from those 

 on blood serum. All were Gram-negative. One strain (menin- 

 gococcus m) remained alive on 2 per cent opsine agar for four 

 months at 18°. Both strains always grew on 1 per cent opsine 

 agar in twenty-four hours, but a little less luxuriantly than on the 

 2 per c'ent medium. 



Five out of the six strains of pneumococcus employed grew on 

 2 per cent opsine agar, four of them nearly as well as on the con- 

 trol medium. The fifth was carried through four transplants on 

 1 per cent opsine agar with rather scanty growth, and was always 

 negative on meat extract peptone agar. In Gram stains the 

 opsine and control cultures were both quite typical, but in the 

 former about half of the organisms were Gram-negative, while on 

 the control all were positive. 



Viability tests on opsine agar and control meat infusion peptone 



agar 



The meningococcus, B. influenzae and B. pertussis were carried 

 through 12 transplants, and the pneumococcus, gonococcus and 

 M. catarrhalis (a.m.) through 8 transplants on opsine. The 

 growths on the last series were compared with those on the control 

 medium, both being 48 hours old. The meningococcus and B. 

 pertussis were grown on 1 per cent, the others on 2 per cent opsine. 

 All of the media were faintly alkaline to litmus. 



Growths at forty-eight hours 



Pneumococcus (80) . . 

 Pneumococcus (690) . 



Gonococcus (287) 



M. catarrhalis (a.m.) 



B. influenzae 



B. pertussis 



Meningococcus (m) . . 

 Meningococcus (200) 



